1. Technical Field
The present invention relates to a semiconductor device, especially a semiconductor device having external terminals, and a method of manufacturing the same.
2. Related Art
Conventional connections between semiconductor chips and electrically connectable members such as a substrate require the formation of a thin metal film for the connection. The thin metal film is generally formed through sputtering or vapor deposition. In the connection using this thin metal film, for example, solder having a high melting point is used. In the case of soldering, the oxide film formed on the surface of the solder makes the wettability and spreadability poor, and defects in mounting (failure in fusion of solder) easily occur between the bonding agent applied to the side to be mounted and the solder at the time of reflow for mounting in accordance with the specifications of the customer. Therefore, it is necessary to take measures against oxidation on the surface of the solder so that defects in mounting have to be prevented.
Japanese Laid-open patent publication No. 2002-203872, for example, discloses a technology for mechanically and physically removing oxide films on the surface of solder bumps provided on electronic parts as external connection terminals using a polishing type cleaner.
In addition, Japanese Laid-open patent publication No. 2000-174059 discloses a technology for removing oxide films on the surface of solder bumps provided on electronic parts as external connection terminals through friction by providing vibration, using an oscillator, to the substrate on which electronic parts are mounted.
In addition, Japanese Laid-open patent publication No. 11-204926 discloses a technology for removing oxide films on the surface of solder balls provided on electronic parts as external connection terminals using an oxide film removing agent made of an organic compound and a diluting agent for the oxide film removing agent.
Furthermore, there is also a technology for removing oxide films through a plasma process.
In the above described technologies for removing oxide films using a polishing type cleaner, a plasma process and an organic compound, however, static electricity may be generated. In the case of ultrasonic bonding as well, static electricity may be generated through friction. Accordingly, there may be a problem where electrostatic breakdown is caused and the quality of the semiconductor chip is lowered.
In addition, the above described problem is not limited to the cases where a semiconductor chip is connected by means of solder, but becomes a common problem in the connection of a semiconductor chip having external connection terminals made of a material other than solder.
Furthermore, solder balls made of a tin-copper alloy based material (melting temperature: approximately 220° C.) have been put into practice in recent years as external connection terminals. This tin-copper alloy based material is easily oxidized in comparison with conventional tin-lead alloy based materials. Accordingly, a problem where defects in mounting (failure infusion of solder) occur has become severe.
The present inventor has recognized that the present invention provides a measure against the oxidation of external connection terminals without generating static electricity so that defects in mounting can be reduced and an increase in the yield of assembly and an increase in the quality of bonding can be achieved.